Glass sheets used as substrates for display applications, e.g., LCDs and organic light emitting diode (OLED) displays, need to have surfaces which are clean and free of particles, films, etc. Extensive washing and drying at the end of the finishing process are often used to clean the glass sheets. Accordingly, efforts have been undertaken to find effective ways of inspecting glass sheet surfaces for determining surface quality.
Extremely thin layers of residue left on glass after washing processes may be measured in nanometers, which do not change the light reflecting, refracting, scattering, polarization enough to be measured using conventional photoelectric sensors. Currently there are no quantitative measurement techniques for large volume high speed surface area cleanliness inspection.